Hi Jim,
I think that the “topcoat while it’s
sticky” method works well especially in the nooks and crannies that are
hard to get to.
Changing the subject a little, with the
availability of good coating systems today, some of the large surfaces that we
sometimes fabricate in stainless steel could probably be done in carbon and painted
with good results. Stainless is beautiful but also very expensive for
homebuilders. It also is more likely to warp (adding more cost in machining)
and is more challenging to weld. There is also debate about its ultimate
strength when welded to a dissimilar material. I’m not saying I don’t
like stainless- I’m just saying that homebuilders could probably apply their
hard earned funds to something else on the boat and get along just fine with a
good hard paint job. I would still use 316 ss for all brackets and fittings
though.
As far as powder coating goes, I powder
coated the steel hatch on my sub with good results so far.
Greg
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of JimToddPsub@aol.com
Sent: Tuesday, May 08, 2012 12:09
PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
Paint.....Cheap or Proper?
Thanks much for adding that
information. I think I'd be late for my own wedding before I'd let an
undercoat harden and then have to sand and tack off the dang thing. It's
a pain to do, and I wouldn't have as much confidence in the long-term adhesion.
Polyurethane, polyester-epoxy, and strait
epoxy have all been materials applied by powder coating. Do you know if
it's been done or would be appropriate for our purposes?
In a message dated 5/8/2012 9:54:59 A.M.
Central Daylight Time, greg@precisionplastics.com writes:
Basically, epoxy is a great moisture barrier but does not weather
very well (it can “chalk out”). That’s why we topcoat it with
urethane. But it is very tough to get good adhesion on top of hardened epoxy
(especially with urethanes). I prefer shooting the topcoat while the epoxy is
still “tacky” but some people let it harden and then scuff it.
Also, polyester based urethanes are harder and weather better than acrylic
based urethanes when used around salt water. The reason to use clear coats is
because of the increased UV protection.
After going through all the effort it takes to build a submarine,
you’ll be glad you put a little extra into a durable paint job.
Greg
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On
Behalf Of JimToddPsub@aol.com
Sent: Tuesday, May 08, 2012 10:27
AM
To: personal_submersibles@psubs.org
Subject: Fwd: [PSUBS-MAILIST]
Paint.....Cheap or Proper?
Scott,
Greg and James are right on. I used to own a business
spaying polyurethane and still have the equipment (except for the spray
booth), and I'm going to take it to a professional shop to do it according
to my specs. Getting it right on the interior is at least as important as
the exterior. You can hose down and wash the exterior; can't do that to
the interior.
Below is a thread from 14 month ago on painting a sub.
It's well worth reading the whole thing.
From: JimToddPsub@aol.com
Reply-to: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Sent: 3/21/2011 2:55:36 P.M. Central Daylight Time
Subj: Re: [PSUBS-MAILIST] Paint.....Cheap or Proper?
One thing I don't completely understand is the need for epoxy
between the primer and the upper coats of polyurethane instead of just applying
more coats of poly. Is it because you can attain greater total
mil thickness with an epoxy sandwich than you can with additional coats of
poly? Is it because the hard epoxy underneath improves the impact
resistance of the poly topcoats?
I've never sprayed epoxy. When spraying polyurethane, we
were always careful to keep the coats thin enough to avoid skinning over and
trapping solvents within the coat. Trapped solvents will create
pinholes. Generally we were spraying a tack coat and two or three
additional coats.
In a message dated 3/21/2011 2:03:06 P.M. Central Daylight Time,
vbra676539@aol.com writes:
Immersion is a long-term consideration, a category we don't fall
into. UV really isn't a large concern for us in Florida, either, as most of the subs I know
about are stored indoors or at least under cover, and a few hours exposure
doesn't seem to do much harm. That said, any boat owner you care to check with
down here will tell you that epoxy SUCKS as a long term outer coating. It
simply will not put up with years of exposure. That doesn't make polyurethane
easier. In fact, it gets harder, as you have to abrade the cured
epoxy tie-coat to ensure a good mechanical bond between it and the
polyurethane top coat.
Jim, I'm sure your guys know their coatings. However, they are
misinformed as to overall serviceability. If you beat up the epoxy, then you
get zinc exposed at best, and your bare hull at worst. Nine times out of ten,
if you scuff the polyurethane, the epoxy underneath will survive and protect
you until you can get your paint brush out again. Each component provides additional
protection, something to be considered over time.
That said, the new coatings available today are so superior to the
old days that you can use just about anything and, with care, do pretty well.
We spend more time on the trailer than we do in the water, so if you pay
attention, then almost anything you use will provide adequate protection.
Except for Alex, of course. He invented a rust maker. Love to see that.
-----Original Message-----
From: kocpnt tds.net <kocpnt@tds.net>
To: personal_submersibles <personal_submersibles@psubs.org>
Sent: Mon, Mar 21, 2011 2:30 pm
Subject: Re: [PSUBS-MAILIST] Paint.....Cheap or Proper?
I'm not sure of the correct answer! I know that it's done and do
not know details, however my paint reps were emphatic. I live in Wisconsin and UV is a much smaller concern than
for Vance etc. so I just used the epoxy.
I would reccomend talking to a knowledgable rep before purchasing.
On Mon, Mar 21, 2011 at 1:13 PM, <jimtoddpsub@aol.com>
wrote:
Jim K,
Thanks much. Regarding polyurethanes, is there a distinction between a few
hours of immersion (2-10) for a small sub versus much longer in the case of a
larger sub, boat bottom, or underwater structure?
Jim T
Sent on the Sprint® Now Network from my BlackBerry®
Date: Mon, 21
Mar 2011 12:54:03 -0500
Subject: Re: [PSUBS-MAILIST] Paint.....Cheap or Proper?
While there some exceptions, (most notebly moisture cure
urethanes) epoxy is almost always the prefered product for corosion protection
especially in immerssion situations. Corrosion protection is largely a function
of mill thickness and heavy epoxy mastics can be applied at 5 - 10 mils DFT dry
film thickness per coat. Most polyurethanes can not be applied over 5 mils. The
rust inhibitive properties are very good with Sherwin-Williams Macropoxy 646
and two full coats will easily cover the blast profile of about 4 mils that you
will probably end up with. If you want great shine topcoating with polyurethane
is good. I know phil does this, however my tech reps tell me that polyurethanes
do not perform well in immersion situations.
Kocourek Industrial Painting
On Mon, Mar 21, 2011 at 10:02 AM, Stewart Gardiner <stew@terminalsolutions.biz>
wrote:
Thanks for clarifying that Jim! I did mean 2
part polyurethane…. Epoxy being a generic term for anything using a
hardener etc J the particular paint brand ive used on
fibreglass boats before is Norglass or Norcoat..
The polyurethane primer came out so well I was
actually contemplating leaving it in primer and not worrying about the top
coat! J but UV protection might not be so good with
the primer…also its slightly porous…
The last time I worked extensively with coatings
was 1983. We were using two-part polyurethanes that cost $250
USD per gallon at that time. Epoxies were considered older
technologies that were becoming obsolete, however I think the term
"epoxy" is being used generically to denote any type of two-part
coating (color and catalyst or hardener).
This is one of the last places I would try to
save money, and I would spend just as much on interior primers and coatings as
exterior for two reasons:
1. Preventing corrosion is a lot better
than trying to cure it, and having to do that (and redo) the inside the
sub can be a bear.
2. After an operation, I can wash down the
exterior with fresh water and whatever else I chose to use. That's not an
option with the interior.
I've also wondered about spraying the entire
exterior with a wax several hours prior to a mission but haven't investigated
that. Seems reasonable.
The first time I sandblasted and painted Snoopy,
I put lots of coats of expensive epoxy on the outside, but had this same
exact thought about the inside. That surely won't get
wet, therefore cheap and ordinary paint should do! Well, when Snoopy
was in Florida the humidity was 100%,
the temperature was something ridiculous, and climbing in and out even
splashed a little salt water inside. With the combination of those three
factors, when I was being towed out to a dive site the inside rusted so fast I
could actually see the rust move. I mean that literally, you could see it
popping up from under the paint, rather like a paper towel that has been
laid over a counter that's sprinkled with water.
I still don't use as expensive a paint on the
inside as the outside, but one paint I've found is economical yet
tough is a two part epoxy for painting garage floors. It's very
thick, giving really good coverage, and resistant to
abrasion. The downside is there aren't any rust preventers in it
because it's intended for concrete, so you want to spray
a base for metals underneath.
The contents of this
e-mail are intended for the named addressee only. It contains information that
may be confidential. Unless you are the named addressee or an authorized designee,
you may not copy or use it, or disclose it to anyone else. If you received it
in error please notify us immediately and then destroy it.
Im going to paint the inside of my battery pods
today. As theoretically, the insides should not get wet, i was thinking
of using just a normal metal paint like Hammerite or something. A
straight forward paint that you would use to paint outdoor railings and things
with. Do you think this will be ok or should i go for the
"proper" 2 part epoxy marine primer? Its just really
expensive.
|